Frequently when I DM I will give my players consumables (i.e. potions and scrolls) in loot drops in place of gold. My intention is to give them more flexibility in strategy during exploration and combat, especially by providing spells most spellcasters deem too "situational" to be useful (for example, a one-use scroll of Gust of Wind might slow down goblin reinforcements in a hallway, or provide extra force to a sail, but otherwise doesn't usually show up in my games).
The problem is: they never use the consumable items. The main reason seems to be the players abstain from using the items, waiting instead for the "perfect time" to use them, only to discover that time never comes, and the item is forgotten long after it is found.
How can I encourage my players to be less frugal with these items and use them more frequently? I thought about giving the items "time limits" (i.e. that potion will only last for one in-game day), but then it is hard to explain how it was still good up until the party found it. I'm also looking for empirical evidence of success in encouraging less frugal item use.
To clarify, I am not looking to force a play-style on my players. If they wish to forgo item use, that is their prerogative. I just want it to be for a reason other than waiting for the "perfect moment".